“An octopus that has entered the pot is content with the small world of its own and enjoys a night’s dream, never suspecting that it might be pulled up in the morning. A man born into this world is like that, too, as he lives a life as brief as a dewdrop. Such a view is presented in this poem. In view of the site, there may be historical allusions, too.” –Koseki

“Isn’t it impossible to imagine that Basho had completely entered the mind of an octopus inside the pot? He became an octopus, so to speak.” -Watsuji

And still another interpretation:

“In the Japanese poetic tradition, those who complain of the shortness of the summer night are, above all, lovers who have to part in the morning. Basho drew upon that traditional mood of romantic love and applied it to the life of an octopus dreaming a short dream in a pot, thereby turning it into humor.” -Yamamoto

The aforementioned haiku and commentary were
translated by Professor Emeritus Makoto Ueda.

Note about the print: Isoda Koryūsai (礒田湖龍斎 1735-1790?) was a Japanese printmaker and painter active from approximately 1764 to 1788. (via Wikipedia)